Contents

Design Goals

OLPC's laptops will be deployed in places where there will be very little or no infrastructure at all. We wanted to make sure that the laptops could connect to other laptops in their vicinity regardless of the presence or not of connectivity infrastructure. We also wanted to help kids share Internet connectivity without any additional infrastructure.

It became very clear that the utility of the usual laptop wired connectivity options (ethernet, modem) will be very limited under those constraints and a relative waste of our limited bill of materials budget. Instead we have to concentrate our resources to increase the utility and functionality of the wireless network adapter.

To achieve our design goals we chose to add self organizing multihop (mesh) networking capabilities to the laptop's network adapter. The constraints imposed by our Mesh Network Details mandate the use of System on Chip (SoC) Wireless Adapter, with the mesh networking protocol running directly on the adapter's CPU.

Mesh Wireless

User Experience

There is complexity in properly configuring the wireless network in the variety of use scenarios that our children will encounter. Our bias is towards making efficient use of the mesh, but in some situations, our infrastructure mode will be used. In those cases, the laptop will offer mesh portal (MPP) services to other laptops nearby. If no mesh or access point is visible, then the laptop will become a mesh point on Channel 1.

We use channels 1, 6, and 11 when possible. This lets us use three channels with essentially no overlap. Wireless routers using any of these three channels appear in the Neighborhood View.

To analyze airtime consumed by a given type of traffic, check this page

Antenna Reliability

The antenna "ears" have been subjected to drop testing in both the open and close positions, and survive multiple drops onto concrete from desk height. They are made of rubber surface over a polycarbonate center section, allowing them to flex upon impact.

In the event of antenna breakage, there are two antennae. A laptop will continue to function satisfactorily with a single ear in a school setting, and should suffer only slight degradation in performance in more remote settings. The ear was redesigned late in the design process (C-build and later) to simplify repair --- replacing an ear now requires the removal of only six screws, thanks to a connector embedded in the rotary hinge.